1. Field of the Invention
The invention relates to novel (1,2-naphthoquinone 2-diazide)sulfonic acid esters of substituted trihydroxybenzophenones and a radiation-sensitive mixture prepared therewith.
The invention also relates to a radiation-sensitive recording material comprising a substrate and a radiation-sensitive layer.
2. Description of Related Art
An important step in the production of electronic components is the imagewise irradiation and subsequent development of a radiation-sensitive layer which has been applied to the material to be patterned. Such a layer may be positive- or negative-working.
In a positive-working layer, photoactive components are generally used which contain (1,2-naphthoquinone 2-diazide) units. A large number of such components, primarily esters of aromatic polyhydroxy compounds and (1,2-naphthoquinone 2-diazide)sulfonic acid are described in the book by Jaromir Kosar: Light-Sensitive Systems, John Wiley + Sons, New York, 1965, pp. 343-351.
Progressive miniaturization in the production of electronic components requires the generation of ever smaller patterns. This necessitates radiation-sensitive photoresists having ever higher resolving power. It is known that the resolution is improved by increasing the content of diazoquinone in the radiation-sensitive layer. See H. M unzel, J. Lux, R. Schulz, "A- and B-Parameter dependent Submicron Stepper Performance of Positive Type Photoresist," Microelectronic Engineering, 6: 421-426, 1987. P. Trefonas III and B. K. Daniels, "New Principle for Image Enhancement in Single Layer Positive Photoresists" Proceedings of SPIE, 771:194-210 (1987), 194-210, points out that compounds containing a plurality of diazonaphthoquinone units achieve higher contrasts and consequently a better resolution.
Frequently used compounds containing a plurality of diazonaphthoquinone units which are often described in patent literature are esters of (1,2-naphthoquinone 2-diazide)-4- and -5-sulfonic acid and polyhydroxybenzophenone, the 2,3,4-trihydroxybenzophenone being preferred among the polyhydroxybenzophenones.
A disadvantage of these esters is, however, their relatively low solubility in the solvents generally used, it not being possible, consequently, to increase their concentration in the radiation-sensitive mixtures to the desired extent. A further increase in the resolving power is therefore not possible by this method. In addition, the resist mixtures prepared with these esters do not have adequate shelf life.
These disadvantages were already known and have been described in JP-A 01-017049. This document discloses improving the shelf life of the resists by using esters of (1,2-naphthoquinone 2-diazide)-5-sulfonic acid and 2,3,4-trihydroxy-2'-methylbenzophenone.